This invention relates to roofing construction, and is more particularly concerned with the transfer and application of molten asphaltic material to roofs. The invention provides an apparatus and process which replaces conventional methods of transferring asphaltic compositions to elevated work areas with an automatic feed system. In addition, uniform application of the asphaltic material to work surfaces is achieved via a number of hand-operable, attachable applicator devices.
In building or repairing a structure, it is conventional practice to cover a roof surface with a liquid roofing composition. This liquid roofing composition may include a mixture of tar, pitch, and bituminous components. For simplicity, this roofing composition will heretofore be referred to as `hot asphalt` when it is in a heated, liquified form.
Traditional practice has been to heat a central supply of this roofing composition in a kettle or tanker located on the ground. When the composition reaches temperatures in excess of 300.degree. F., it changes into a hot asphalt state. One type of heating device used to warm roofing material is described in the Mason U.S. Pat. No. 5,099.824, in which water heated by a natural gas source is allowed to circulate around drums containing said roofing material. Another similar apparatus is disclosed in the U.S. Pat. No. 5,120,217 issued to O'Brien et al. This particular asphalt heating device, which includes a conveyor means in the form of a screw discharge feed, heats initially cold asphaltic material to a temperature between 275.degree. and 300.degree. F., and maintains it at that temperature until it is used. The slow and even heating operation proposed by the O'Brien et al. invention avoids overheating, segregation, oxidation, or ignition of the asphaltic material.
Transferal of the hot asphalt to the elevated roof surfaces has relied, in large part, on labor intensive techniques and apparatus. If the working surface area of the roof to be coated is relatively small, quantities of the hot asphalt are manually carried up steps or ladders to hot luggers. The hot asphalt is then poured into individual mop carts or spreaders, and subsequently applied to the roof surfaces. Alternatively, if the area of the roof is relatively large, crude pump mechanisms are routinely employed to automatically transfer the hot asphalt from the ground based kettle to a hot lugger on the roof.
These conventional transfer practices have led to numerous problems. The first, and possibly the most evident, is one of inefficiency. If only a few workers are engaged in a typical roofing operation, they will have to alternate between applying the hot asphalt material to the roof surface and transferring the same from the ground to a place of easy access. Since the major portion of the hot asphalt material must remain on the ground to be heated in the central kettle or tanker during an application, this back and forth routine can ultimately turn a seemingly small roofing job into a tedious and time consuming operation. In order to allow such a roofing application to become a more continuous and non-interrupted process, quantities of the hot asphalt will need to be regularly transferred to the roof top at small time intervals. As conventional methods dictate, this can only be accomplished with the addition of more laborers.
Still another drawback associated with these conventional hot asphalt transfer practices is one of safety. Since the hot asphalt material can reach temperatures starting from 275.degree. F. and exceeding 500.degree. F., direct contact with the material often results in first to third degree burns. Manually carrying the hot asphalt up ladders to roof surfaces is an exceptionally dangerous technique, and one which has resulted in serious injuries to scores of laborers. Once the molten material is on the roof surface, danger of contact with and exposure to the hot asphalt continues as it is dumped into hot luggers, poured into mop carts, and finally, applied to roof surfaces.
Once the hot asphalt has been transferred to a readily accessible place, the roof workers must apply the hot asphalt to the roof surface. The primary object in this stage is to apply a sufficient and uniform coat of the material onto the surface. If too little hot asphalt is applied at certain points, those same inadequately coated areas may become vulnerable to leaking as the roof ages. If too much hot asphalt is applied, both time and material are wasted. Also, since the hot asphalt is subject to `setting-up` when it is out of communication with a heat source (especially in cold weather conditions), the roofers are typically forced to apply the material rather speedily. An old but nonetheless acceptable technique in this application stage is to first dip mops into mop buckets containing the hot asphalt material, and then to manually spread the material in a mopping-like manner. Another technique is to dump a quantity of hot asphalt material directly onto the roof surface, and to then spread it using a combination of mops, rakes, and coat devices.
In his two U.S. Pat. Nos. 4,165,192 and 4,265,559, Mellen introduces a novel hot asphalt spreading machine (improved in his second patent) which assists in this application process. The spreading apparatus includes an insulated chamber for containing an amount of hot asphalt, a pipe system extending from the insulated chamber and having a number of port holes for regulating the flow of the hot asphalt from the container, and a turnable valve and valve control handle for actuating and controlling the hot asphalt flow. Once the hot asphalt is ejected from the port holes located along the pipe system, it is evenly spread by either teasing chains or screens, and finally, by a trailing rake. These spreading tools are all dragged immediately behind the path of newly ejected hot asphalt material.
Although the Mellen spreading machine does make the application of the hot asphalt a more controlled and simplified process, his machine has several shortcomings. First, there is no provision for or suggestion of a feed system which would automatically transfer the hot asphalt to the spreading device. Instead, his machine needs to be manually refilled every time the insulated chamber is emptied. Even when compared to traditional techniques, this is rather time consuming. Second, the insulated chamber in his machine can only keep the hot asphalt in a liquid state for a certain amount of time. In this sense, a delay in the application process will cause the hot asphalt in the container to harden, and coating will become difficult if not impossible. In order to avoid these problems, the hot asphalt will still need to be applied relatively quickly, especially during winter applications. Also, since the hot asphalt needs to be manually poured into the insulated chamber through a funnel opening, danger of exposure to the molten material does still exist.
A number of hand-held devices used to apply heated substances have not only been invented, but are also thoroughly accounted for in the prior art. The U.S. Pat. No. 1,491,459 issued to Bernat teaches a hand-held brush device used to supply garments with steam in a continuous and thin stream. The Bernat steam brush includes an insulated hand grip that allows the user to comfortably manipulate the device without danger of being burned. A molten material dispenser used to heat and apply molten wax for the creation of pattern molds is the subject of the Ghim U.S. Pat. No. 4,432,715. The Ghim invention includes a storage container for the wax, means to heat the wax, means to control the wax flow, and means to transfer the wax between the storage container and an applicator portion.
Since the Dernat and Ghim inventions are respectively directed towards spraying steam onto fabrics and applying wax to molds, they are not capable of transferring and applying hot asphalt material. Neither have discharge ports designed to spray hot asphalt. Moreover, the small size of the Ghim device renders it completely impractical for large scale roofing applications.
What is needed is a portable device which can automate the transfer of a steady supply of the hot asphalt material to a roof surface, keep the hot asphalt supply heated so that it remains in a readily spreadable form, and automatically transfer the hot asphalt material to any one of a number of hand-held applicators. Such a device would greatly improve both the efficiency and safety associated with conventional roofing practices.